High-temperature ovens, or reactors, are used to process semiconductor substrates from which integrated circuits are made for the electronics industry. A substrate, typically a circular silicon wafer, is placed inside a reaction chamber within the reactor. Typically, the wafer is supported upon a wafer holder enclosed within a reaction chamber, and the wafer and wafer holder are heated to high temperatures. In one exemplary process, a reactant gas is passed over the heated wafer, causing the chemical vapor deposition (CVD) of a thin layer of the reactant material on the wafer. Through a variety of deposition, etching, photolithography, doping, annealing, and other processes in other equipment, such layers are made into integrated circuits, producing from hundreds to millions of integrated devices, depending on the size of the wafer and the complexity of the circuits.
One factor affecting the quality of a processed wafer is the number of contaminant particles on the wafer, which depends upon the degree of particulate contamination within the semiconductor processing equipment, and particularly the reaction chamber. In order to reduce contamination, it is important to effectively seal the various chambers inside the processing equipment from the outer environment and in some cases from each other during processing. In some reactors, a slit-type gate valve, or “slit valve,” is utilized to seal the reaction chamber from the environment. In this Background and Summary of the Invention, such valves are discussed in the context of sealing the reaction chamber from other chambers of the semiconductor processing equipment. However, it will be understood that such valves can be used in a variety of different locations, such as, for example, between load-lock chambers and wafer transfer chambers.
In one common configuration, the slit valve resides within a passage connected to the reaction chamber, the passage sized and adapted for the transfer of semiconductor wafers into and from the chamber. The slit valve commonly includes a valve housing that defines a portion of the aforementioned passage. The valve includes an actuator plate positioned within a slot in the valve housing, the actuator plate being moveable within the slot in a direction generally transverse to the passage. In an open position of the slit valve, the actuator plate is positioned to permit the transfer of semiconductor wafers into and from the reaction chamber through the passage. In a closed position of the slit valve, the actuator plate is positioned to fluidly seal (i.e., to seal such that fluids cannot pass through) the passage, in order to isolate and limit particulate contamination of the reaction chamber. In the closed position of the slit valve, the actuator plate prevents fluid from flowing through the passage across the actuator plate. Typically, the actuator plate includes a compliant sealing material that seals against a sealing surface on the inner surface of the valve housing. In a typical cycle of use, the slit valve is first opened to permit the removal of a processed wafer from the reaction chamber. The processed wafer is removed through the passage, and a new substrate is inserted into the reaction chamber for processing. The slit valve is then closed.
One problem associated with conventional slit valves for semiconductor reactors is that debris within the passage, such as broken wafer fragments, shards, and particulate contaminants, tend to enter the slot within which the actuator plate is received. This often occurs when the valve is open, as wafers and equipment used for transferring the wafers, such as, for example, spatulas or Bernoulli wands, move through the passage. Such debris can even include particles that flake off of the wafers or even the wafer transfer equipment. The debris can eventually build up in the slot, leading to the generation of particles as the actuator plate grinds against the debris. This causes particle counts to rise to undesirable levels. Also, the debris that builds up within the slot can damage the sealing material on the actuator plate, leading to a reduction in sealing effectiveness. Particles on the edges of the actuator plate can additionally damage (e.g., scratch) the sealing surface on the inner surface of the passage/valve housing, also leading to reduced sealing effectiveness.
Thus, it is a principle object and advantage of the present invention to overcome the above-described problems associated with slit valves for semiconductor processing apparatus.
In one aspect, the present invention provides a slit valve comprising a passage, an actuator plate, and a protective cover. The passage is sized and adapted for the transfer of a semiconductor substrate through the passage. The passage has first and second walls generally opposing one another. The first wall has a slot oriented generally transverse to the passage. The actuator plate is received within and configured to translate within the slot. The actuator plate has a first position in which it permits the transfer of a substrate through the passage, and a second position in which it blocks the passage. The protective cover is configured to substantially prevent debris within the passage from entering the slot when the actuator plate occupies its first position.
In another aspect, the present invention provides a semiconductor processing apparatus that includes a slit valve comprising a passage and an actuator plate. The passage has first and second walls generally opposing one another, the first wall having a slot. The actuator plate is received within and configured to translate within the slot. The actuator plate has a first position in which it permits transfer of a substrate through the passage, and a second position in which it blocks the passage. The plate is configured to selectively cover the slot when the actuator plate occupies its first position.
In another aspect, the present invention provides an apparatus for processing a semiconductor substrate. The apparatus comprises a first chamber, a second chamber, a passage connecting the first and second chambers, an actuator plate, and a protective cover. The passage is sized and adapted to permit the transfer of a substrate between the first and second chambers. The passage has first and second walls generally opposing one another, the first wall having a slot. The actuator plate is received within and configured to translate within the slot. The actuator plate has a first position in which it permits the transfer of a substrate from the first chamber through the passage into the second chamber. The actuator plate also has a second position in which it blocks the passage. The protective cover is hingedly secured to the first wall of the passage proximate the slot. The cover has a closed position in which it substantially prevents debris within the passage from entering the slot. The cover is permitted to occupy its closed position when the actuator plate occupies its first position. The cover has an open position, which it occupies when the actuator plate occupies its second position.
In another aspect, the present invention provides an apparatus for processing a semiconductor substrate, comprising a chamber configured to enclose a semiconductor substrate, a region outside the chamber, a passage connecting said chamber and said region, an actuator plate, and a protective cover. The passage is sized and configured for transferring a substrate through the passage between said chamber and said region. The passage has first and second walls generally opposing one another, the first wall having a slot oriented generally transverse to the passage. The actuator plate is received within and translatable within the slot in the first wall. The actuator plate has a first position in which it permits the transfer of a substrate from said region through the passage into said chamber. The actuator plate also has a second position in which it blocks the passage. The protective cover is secured to the actuator plate proximate an end of the actuator plate. The cover is configured to substantially prevent debris within the passage from entering the slot when the actuator plate occupies its first position.
In yet another aspect, the present invention provides a method of transferring a substrate from a region outside a chamber of a semiconductor processing system to within the chamber, wherein the processing system includes a passage connecting said region and the chamber. According to the method, an actuator plate is provided in a position sealing the passage. The actuator plate is withdrawn into a slot extending from walls of the passage, thereby opening the passage. When the actuator plate is withdrawn into the slot, a protective cover is positioned over the slot. When the actuator plate is withdrawn into the slot, a substrate is transferred from said region through the passage into the chamber.
For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described above and as further described below. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.
All of these embodiments are intended to be within the scope of the invention herein disclosed. These and other embodiments of the present invention will become readily apparent to those skilled in the art from the following detailed description of the preferred embodiments having reference to the attached figures, the invention not being limited to any particular preferred embodiment(s) disclosed.